Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India

Abstract

A i i s t k a c t .Avoidable losses and economic injury levels (ElLs) were computed for the sorghum head bug. Calocoris amjustatus Leth., on three cuitivars during three rainy seasons {1985-1987) at IGRISAT. Grain yield in plots i)rotected with 2-5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthe^is and the dough stage was significantly higher than in untreated plots, with cost benefit ratios > 1. Plots that were not protected aL half-ail thesis and/or complete-an thesis, and at milk and dough siages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three io four sprays between coniplete-aiuhesis and the dough stage prevented a significant reduction in grain quality. Mead bug density at hall-ainhesis. eomplete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different siages explained -hi 94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect elici ts of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. M aximum avoidable losses were recorded in cultivar I CSV 1 (88-6%), followed by GSIf 1 (69-9%). and CSII 5 {:>3-9% in lf)H(i and 554)% in 1987). Loss in grain yield/ha due to one insect/panicle at hall-anthesis and that based on natural increase,-were 548 tind 232 kg in CSII 5 (hiring 1986 and 1987, respectively. 251 kg in IC.SV I, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1 :! ranged from 1-3 1-4 insects/panicle for CSH I. 0-4 for I CSV 1, and O-I-(M) and 0-2-0-! for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.

Genotypic effects of sorghum accessions on fecundity of sorghum head bug, Calocoris angustatus Lethiery

“…In different parts of India, avoidable losses of 7-84% due to head bugs have been estimated (Leuschner & Sharma, 1983) . Under experimental conditions, 55-84% losses have been recorded in the commercial cultivars CSH 5, ICSV 1, and CSH 1 (Sharma & Lopez, 1989) .…”

Influence of panicle compactness and host plant resistance in sequential plantings on population increase of panicle‐feeding insects inSorghum bicolor(L.) Moench

“…Severe damage by head bugs and head caterpillars during the rainy season predisposes the developing grain to grain mould infection (Sharma et al, 1992a). Head-bug-damaged grain is of poor nutritional quality, may become unfit for human consumption (Sharma and Lopez, 1989;Sharma etal., 1993 a, b), and fetches half the price of grain produced during the post-rainy season.…”

Interactions between panicle size, insect density, and environment for genotypic resistance in sorghum to head bug, Calocoris angustatus

“…Both adults and nymphs suck the sap from the developing grain, resulting in tanning and shriveling of the damaged grain. This results in a severe loss in grain yield and quality (Sharma & Lopez, 1989).…”